Apparatuses and methods for performing spectroscopic analysis of a subject

ABSTRACT

This invention relates to a light delivery and collection device for performing spectroscopic analysis of a subject. The light delivery and collection device comprises a reflective cavity with two apertures. The first aperture is configured to receive excitation light which then diverges and projects onto the second aperture. The second aperture is configured to be applied close to the subject such that the reflective cavity substantially forms an enclosure covering a large area of the subject. The excitation light enters and interacts with the covered area of the subject to produce inelastic scattering and/or fluorescence emission from the subject. The reflective cavity has a specular reflective surface with high reflectivity to the excitation light as well as to the inelastic scattering and/or fluorescence emission from the subject. The reflective cavity reflects the excitation light that is reflected and/or back-scattered from the subject and redirects it towards the subject. This causes more excitation light to penetrate into a diffusely scattering subject to produce inelastic scattering and/or fluorescence emission from inside of the subject hence enabling sub-surface measurement. In addition, the reflective cavity reflects the inelastic scattering and/or fluorescence emission from the subject unless the inelastic scattering and/or fluorescence emission either emits from the first aperture of the reflective cavity to be measured with a spectrometer device, or re-enters the subject at the second aperture. This multi-reflection process improves the collection efficiency of the inelastic scattering or fluorescence emission from the subject.

REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. application Ser. No.15/378,156, entitled “LIGHT DELIVERY AND COLLECTION DEVICE FOR MEASURINGRAMAN SCATTERING OF A SAMPLE”, filed on Dec. 14, 2016, by Jun Zhao, XinJack Zhou, and Sean Xiaolu Wang, which is a continuation-in-part of U.S.application Ser. No. 15/349,510, entitled “LIGHT DELIVERY AND COLLECTIONDEVICE FOR MEASURING RAMAN SCATTERING OF A SAMPLE”, filed on Nov. 11,2016, by Jun Zhao and Xin Jack Zhou. The subject matter of theaforementioned U.S. applications is hereby incorporated herein byreference.

FIELD OF THE INVENTION

This invention generally relates to a light delivery and collectiondevice, and more specifically to a light delivery and collection devicefor performing spectroscopic analysis of a subject.

BACKGROUND

Optical spectroscopy measures the interaction of light, especiallymonochromatic light with a material to produce a spectrum characteristicof the material. Such interaction includes inelastic scatteringprocesses, such as Raman and Brillouin scattering, and fluorescenceemission process. Optical spectroscopy has been demonstrated to be apowerful non-invasive analytical technology for materialcharacterization and identification.

Conventional optical spectroscopy generally utilizes a well-focusedlaser beam to produce inelastic scattering and/or fluorescence signalfrom the sample. This approach has the apparent advantage of relativelyhigh efficiency in signal excitation and collection. However, it alsosuffers from the following drawbacks. First, only a small volume of thesample is measured. Thus the collected optical spectra may not be veryrepresentative, especially for some non-uniform samples. Second, thetightly focused laser beam may cause damage to some delicate samples.Third, for diffusely scattering samples which are not transparent to thelaser beam, this approach will only measure the inelastic scatteringand/or fluorescence signal from the surface layer of the sample. Themajority of the material underneath the surface will be almostcompletely out of reach.

There thus exists a need for an improved light delivery and collectiondevice for performing optical spectroscopy, which not only allows themeasurement of a large area of the sample but also enables sub-surfaceoptical signal excitation and collection.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide a light deliveryand collection device for performing spectroscopic analysis of asubject. The light delivery and collection device comprises a reflectivecavity with two apertures. The first aperture is configured to receiveexcitation light which then diverges and projects onto the secondaperture. The second aperture is configured to be applied close to thesubject such that the reflective cavity substantially forms an enclosurecovering a large area of the subject. The excitation light enters andinteracts with the covered area of the subject to produce inelasticscattering and/or fluorescence emission from the subject. The reflectivecavity has a specular reflective surface with high reflectivity to theexcitation light as well as to the inelastic scattering and/orfluorescence emission from the subject. The reflective cavity reflectsthe excitation light that is reflected and/or back-scattered from thesubject and redirects it towards the subject. This causes moreexcitation light to penetrate into a diffusely scattering subject toproduce inelastic scattering and/or fluorescence emission from inside ofthe subject hence enabling sub-surface measurement. In addition, thereflective cavity reflects the inelastic scattering and/or fluorescenceemission from the subject unless the inelastic scattering and/orfluorescence emission either emits from the first aperture of thereflective cavity to be measured with a spectrometer device, orre-enters the subject at the second aperture. This multi-reflectionprocess improves the collection efficiency of the inelastic scatteringand/or fluorescence emission from the subject.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying figures, where like reference numerals refer toidentical or functionally similar elements throughout the separate viewsand which together with the detailed description below are incorporatedin and form part of the specification, serve to further illustratevarious embodiments and to explain various principles and advantages allin accordance with the present invention.

FIG. 1A-C illustrates a first exemplary embodiment of the light deliveryand collection device having a reflective cavity for Raman scatteringexcitation and collection as well as a receptacle for receiving a probe;

FIG. 2 illustrates a second exemplary embodiment of the light deliveryand collection device having a reflective cavity for Raman scatteringexcitation and collection as well as a receptacle for receiving anoptical fiber or fiber bundle;

FIG. 3 illustrates a variation of the first exemplary embodiment of thelight delivery and collection device, which has a differently shapedreflective cavity;

FIG. 4 illustrates a scheme of utilizing the first exemplary embodimentof the light delivery and collection device for measuring thetransmissive Raman scattering of a diffusely scattering sample;

FIG. 5 illustrates a slightly different scheme of utilizing the firstexemplary embodiment of the light delivery and collection device formeasuring the transmissive Raman scattering of a diffusely scatteringsample;

FIG. 6 illustrates another scheme of utilizing the first exemplaryembodiment of the light delivery and collection device for measuring theRaman scattering of a diffusely scattering sample;

FIG. 7 illustrates a third exemplary embodiment of the light deliveryand collection device, which has a reflective cavity that is formed by asolid optical material with a reflective coating;

FIG. 8 illustrates a slight variation of the third exemplary embodimentof the light delivery and collection device;

FIG. 9A-D shows the measured Raman spectrum of a sodium benzoate samplecontained in a plastic bottle, as well as the Raman spectrum of theplastic bottle and the Raman spectrum of the sodium benzoate sample forcomparison;

FIG. 10A-C shows the measured Raman spectrum of a D(+)-Glucose samplecontained in a brown envelope, as well as the Raman spectrum of thebrown envelope and the Raman spectrum of the D(+)-Glucose sample forcomparison; and

FIG. 11A-C shows the Raman spectrum of a coated ibuprofen tablet sampleobtained in three different measurement modes.

Skilled artisans will appreciate that elements in the figures areillustrated for simplicity and clarity and have not necessarily beendrawn to scale. For example, the dimensions of some of the elements inthe figures may be exaggerated relative to other elements to help toimprove understanding of embodiments of the present invention.

DETAILED DESCRIPTION

Before describing in detail embodiments that are in accordance with thepresent invention, it should be observed that the embodiments resideprimarily in combinations of method steps and apparatus componentsrelated to a light delivery and collection device for performingspectroscopic analysis of a subject. Accordingly, the apparatuscomponents and method steps have been represented where appropriate byconventional symbols in the drawings, showing only those specificdetails that are pertinent to understanding the embodiments of thepresent invention so as not to obscure the disclosure with details thatwill be readily apparent to those of ordinary skill in the art havingthe benefit of the description herein.

In this document, relational terms such as first and second, top andbottom, and the like may be used solely to distinguish one entity oraction from another entity or action without necessarily requiring orimplying any actual such relationship or order between such entities oractions. The terms “comprises,” “comprising,” or any other variationthereof, are intended to cover a non-exclusive inclusion, such that aprocess, method, article, or apparatus that comprises a list of elementsdoes not include only those elements but may include other elements notexpressly listed or inherent to such process, method, article, orapparatus. An element proceeded by “comprises . . . a” does not, withoutmore constraints, preclude the existence of additional identicalelements in the process, method, article, or apparatus that comprisesthe element.

FIG. 1A illustrates a first exemplary embodiment of the light deliveryand collection device, which is configured to deliver excitation lightto a large area of a sample and collect the Raman scattered lightgenerated thereof. The light delivery and collection device 100comprises a reflective cavity 102 which is made of a material havinghigh reflectivity to the excitation light and the Raman scattered light.Such material can be metal materials, e.g. gold, silver, copper, andaluminum, etc. The surface of the reflective cavity is preferablypolished to produce specular reflection to the excitation light and theRaman scattered light. Alternatively, the reflective cavity 102 may havea surface coating with high reflectivity to the excitation light and theRaman scattered light. Such surface coating can be a metal coating whichexhibits high reflection in a broad range of wavelengths. Or it can be adielectric coating, which has a customized reflection wavelength range.The latter one may reflect only the wavelengths of interest thusrejecting stray light which does not overlap with the excitation lightand the Raman scattered light in wavelength. The surface coating ispreferably a smooth coating to produce specular reflection to theexcitation light and the Raman scattered light. The reflective cavity102 may be made of a flexible material such that it can accommodatevariously shaped sample surfaces.

The light delivery and collection device 100 further comprises areceptacle 118 which is configured to receive a probe 120. The probe 120comprises one or more optical components 122, such as optical lenses,mirrors, filters, beam splitters, optical fibers, etc., which receiveexcitation light from a light source, such as a laser light source (notshown) and focus the excitation light at a first aperture 104 of thereflective cavity 102 and thereby deliver the excitation light 114 intothe reflective cavity 102. The aperture 104 preferably has a size assmall as possible, but large enough to pass unobstructed the excitationlight and the Raman light collectable by the probe 120. The excitationlight 114 diverges and projects onto a second aperture 106 of thereflective cavity 102, which preferably has a size much larger than thefirst aperture 104, and more preferably, at least two times as large asthe first aperture 104 in area and covers an area of at least a fewsquare millimeters. The second aperture 106 of the reflective cavity 102is configured to be applied close to the sample 108 such that thereflective cavity 102 substantially forms an enclosure covering a largearea of the sample 108, where the excitation light 114 enters andproduces Raman scattered light 116 from the covered area of the sample108. By collecting the Raman scattering from a large volume of thesample, the intensity of excitation light on the sample is reduced toavoid sample damage. In the meantime, the collected Raman spectrum ismore representative, especially for non-uniform samples. Here the sample108 can be diffusely scattering samples, such as pharmaceuticals,powders, biological tissues, etc. or even samples having multiple layersof different materials. In the example as shown in FIG. 1A, the sample108 is a diffusely scattering sample having a surface layer 110 and asub-surface layer 112, e.g. a container with powder samples inside. Thesample 108 reflects and/or scatters the excitation light 114, eitherthrough elastic scattering or inelastic scattering (i.e. Ramanscattering and Brillouin scattering) back into the reflective cavity102. The reflective cavity 102 reflects the excitation light that isreflected and/or back-scattered from the sample and redirects it towardsthe sample. This causes more excitation light to penetrate into thediffusely scattering sample to produce Raman scattering from thesub-surface layer 112 of the sample 108. In addition, the reflectivecavity 102 reflects the Raman scattered light from the sample unless theRaman scattered light either emits from the first aperture 104 to becollected by the probe 120 and then measured with a spectrometer device(not shown) to obtain a Raman spectrum of the sample 108, or re-entersthe sample 108 and be re-scattered by the sample 108 at the secondaperture 106. This multi-reflection process improves the collectionefficiency of the Raman scattered light from the sample. In thisexample, the excitation light 114 penetrates through the surface layer110 of the sample 108 with the aid of the reflective cavity 102 andproduces Raman scattering from the sub-surface layer 112 of the sample108. Hence the measured Raman spectrum contains the characteristicinformation of both the surface layer 110 and the sub-surface layer 112of the sample 108. In a separate step, the light delivery and collectiondevice 100 can be removed and the excitation light from the probe 120 isdirectly focused onto the surface layer 110 of the sample 108 to measurea Raman spectrum of the surface layer 110. The latter Raman spectrum canbe mathematically extracted from the previously measured Raman spectrumto obtain a Raman spectrum of the sub-surface layer of the sample. Theenhanced excitation and collection efficiency of the Raman scatteredlight as provided by the reflective cavity hence enables sub-surfaceRaman scattering measurement.

Optically, the reflective cavity serves three purposes, including (i) toprovide a large sampling area; (ii) to maximize signal collection bymeans of multiple reflection and scattering as explained previously; and(iii) to isolate the sampled area from ambient light which wouldotherwise contaminate the signal. The size of the sampling area shouldbe determined by the specific sampling requirement. For example, if thesample is heterogeneous and the goal is to obtain a betterrepresentation of the sample in whole, the sampling area should be madeat least several times larger than the grain size of the sample. If thepurpose is to measure sub-surface sample through a layer of packagingmaterial, then the linear size of the sampling area should be severaltimes the thickness of the packaging material. With the desired samplingarea determined, FIG. 1B and FIG. 1C further illustrate the designconsiderations of the reflective cavity to achieve maximum signalcollection. Referring to FIG. 1B, the excitation light beam 114 from theprobe 120 is focused by the optical components 122 at the first aperture104, and then diverges and projects onto the second aperture 106,covering an initial illumination area 130. The light beam 116collectable by the probe optics similarly projects a collection area132. The collection area 132 and the initial illumination area 130 maybe different in size. With the probe optics fixed, the minimum size ofthe first aperture 104 and the divergence angles of both beams aredetermined. For maximum collection efficiency, the size of the firstaperture 104 should be made as small as possible without obstructing theexcitation and collection beams, that is, just large enough to encircletheir beam waists at the first aperture 104. If it is made much larger,scattered excitation light and Raman light falling on the area outsidethe collection beam waist but inside the first aperture will exit thefirst aperture 104 without being collected by the probe 120. Todetermine the size of the second aperture 106 for maximum signalcollection, one shall first consider that the light outside the apertureis blocked, so the aperture should be at least the size of the desiredsampling area. Next, the inevitable loss at each reflection by thereflective cavity 102 and at each scattering by the sample 108 must beconsidered. For maximum collection efficiency, the Raman scattered lightshould be allowed to exit the first aperture 104 and to be collected bythe probe 120 by going through as few rounds of reflection andscattering as possible. If the second aperture 106 is made larger thanthe projected area 132, Raman light emerging from the area outside theprojected area 132 cannot be captured by the probe 120 without goingthrough more reflection and scattering, which will result in reducedefficiency and limit the effective sampling area to area 132. Thereforethe sampling area is the smaller of area 132 and the second aperture106. On the other hand, the angle of collection 134 as shown in FIG. 1Cfor signal light from the second aperture 106 is proportional to thecollection beam size at the first aperture 104 and inverselyproportional to the cavity length. The larger this angle is, the higherthe collection efficiency. Therefore, the cavity length should be madeas short as possible, without reducing the projected area 132 to belowthe required sampling area. These factors combine to provide that foroptimal efficiency, the size of the second aperture 106 should be equalto the desired sampling area, and that the cavity length should be suchthat the projected area 132 is equal to the size of the second aperture106. Preferably, the second aperture 106 of the reflective cavity 102 isat least two times as large as the first aperture 104 in area.

FIG. 2 illustrates a second exemplary embodiment of the light deliveryand collection device. Here the light delivery and collection device 200comprises a reflective cavity 202 having a similar structure as thereflective cavity 102 in FIG. 1A, as well as a receptacle 218 which isconfigured to receive one or more optical fibers or fiber bundles 220.The optical fiber or fiber bundle terminates at the proximity of a firstaperture 204 of the reflective cavity 202 so as to deliver theexcitation light from a light source (not shown) into the reflectivecavity 202. In a similar way as shown in FIG. 1A, the excitation light214 excites Raman scattering from the sample 208 at a second aperture206 of the reflective cavity 202. The reflective cavity 202 reflects theexcitation light that is reflected and/or back-scattered from the sampleand redirects it towards the sample. In addition, it reflects the Ramanscattered light from the sample unless the Raman scattered light eitheremits from the first aperture 204 to be collected by the probe 220 andthen measured with a spectrometer device (not shown) to obtain a Ramanspectrum of the sample 208, or re-entered sample 208 and be re-scatteredby the sample 208 at the second aperture 206. The fiber bundle 220 maycomprise multiple optical fibers 222. A portion of the fibers, e.g. thefiber in the center of the bundle may be used for delivering theexcitation light while the other portion of the fibers, e.g. the fibersat the periphery of the bundle may be used for collecting the Ramanscattered light.

The reflective cavity of the light delivery and collection device maytake different shapes, e.g. cylindrical shape, conical shape, sphericalshape, or paraboloidal shape, etc. In a slight variation of the lightdelivery and collection device as shown in FIG. 3, the reflective cavity302 of the light delivery and collection device 300 is spherically orparaboloidal shaped. The special shape may favorably reflect the lightinto certain directions hence increasing the excitation and collectionefficiency of the Raman scattering in those directions. In addition, thereflective cavity 302 may comprise an optical window 324 covering itssecond aperture 306, thus preventing the surface of the cavity frompossible contamination from the sample 308. The optical window 324 canbe a flexible membrane such that the second aperture 306 of thereflective cavity 302 can accommodate variously shaped sample surfaces.The optical window 324 is preferably transparent to the excitation lightand the Raman scattered light, and the thickness of the optical window324 should be thin enough to avoid causing excessive insertion loss tothe excitation light and the Raman scattered light. By selecting anappropriate material for the optical window 324, it is also possible toutilize the Raman scattering from the optical window as a reference forcalibrating the wavelength (or Raman shift) of the measured Ramanspectrum.

In yet another variation of the light delivery and collection device,the relative position of the first and second aperture of the reflectivecavity may be adjusted. For example, the first aperture may be off-axisfrom the center of the second aperture such that the excitation lightobliquely illuminates the sample. The reflective cavity may have anadditional aperture for outputting the Raman scattered light. Theposition of this aperture on the reflective cavity may be optimized, forexample, to minimize the percentage of the collected Raman scatteringsignal from the surface material of the sample and maximize thepercentage of the collected Raman scattering signal from the sub-surfacematerial of the sample. Alternatively, the additional aperture may beused to deliver another excitation light of different wavelength toexcite Raman scattering from the sample. In addition, the reflectivecavity may be filled with an optical medium, such as a gas or liquidmedium, for modifying the optical property of the excitation light andthe Raman light.

FIG. 4 illustrates a scheme of utilizing the first exemplary embodimentof the light delivery and collection device for measuring thetransmissive Raman scattering of a diffusely scattering sample. In thisexample, two of such devices are utilized. One device is used fordelivering the excitation light to one side of the sample, and anotherdevice is used for collecting the Raman scattered light from theopposite side of the sample. Referring to FIG. 4, the light deliverydevice 400 has a receptacle 418 to receive a probe 420 and a reflectivecavity 402 with its first aperture 404 in communication with the probe420 to receive the excitation light 414. The second aperture 406 of thelight delivery device 400 is applied close to one side of the sample 408such that the reflective cavity 402 of the light delivery device 400substantially forms an enclosure covering a large area of the sample toexcite Raman scattered light 416 thereof. The light collection device430 has a reflective cavity 432 with its second aperture 436 appliedonto the opposite side of the sample 408 such that the reflective cavity432 collects the Raman scattered light that transmits through the sample408 and delivers it through the first aperture 434 of the reflectivecavity 432 to a probe 440 in a receptacle 438 to be analyzed by aspectrometer device (not shown). The reflective cavity 402 of the lightdelivery device 400 enhances the Raman excitation and collectionefficiency by reflecting back into the sample the majority of excitationlight and Raman scattered light that are reflected and/or scattered backby the sample until they transmit through the sample. The reflectivecavity 432 of the light delivery device 430 functions similarly byreflecting back the excitation light and Raman scattered light which donot fall on its exit aperture, i.e. the first aperture 434. In a slightvariation of the present scheme, the light delivery device 400 may alsobe used for collecting the back scattered Raman light from the sample408 in a similar way as shown in FIG. 1A. The spectra of the backscattered Raman light and the forward scattered Raman light may be usedtogether to analyze the composition of the sample 408.

FIG. 5 illustrates a slightly different scheme of utilizing the firstexemplary embodiment of the light delivery and collection device formeasuring the transmissive Raman scattering of a diffusely scatteringsample. Here the excitation light 514 is directly delivered onto oneside of the sample 508 to excite Raman scattered light 516 from thesample. The excitation light 514 can be either collimated, orconverging, or diverging. A light collection device 530 with a similardesign as shown in FIG. 1A is employed to collect the Raman scatteredlight 516 that transmits through the sample 508.

In a similar manner, the light delivery and collection device as shownFIG. 2 and FIG. 3 may be used for measuring the transmissive Ramanscattering of transparent or diffusely scattering samples.

FIG. 6 illustrates another scheme of utilizing the first exemplaryembodiment of the light delivery and collection device for measuring theRaman scattering of a diffusely scattering sample. In this scheme, thedevice is used for delivering the excitation light to the sample.Similar to the light delivery and collection device as shown in FIG. 1A,the light delivery device 600 has a receptacle 618 to receive a probe620 and a reflective cavity 602 with its first aperture 604 incommunication with the probe 620 to receive the excitation light 614.The second aperture 606 of the light delivery device 600 is appliedclose to the sample 608 such that the reflective cavity 602 of the lightdelivery device 600 substantially forms an enclosure covering a largearea of the sample to excite Raman scattered light 616 thereof. Thereflective cavity 602 reflects the excitation light that is reflectedand/or back-scattered from the sample and redirects it towards thesample. This causes more excitation light to penetrate into thediffusely scattering sample to produce Raman scattering from inside ofthe sample. The Raman scattered light which transmits through the sample608 is collected by a probe 630 and then delivered into a spectrometerdevice (not shown) for spectral analysis. The back-scattered Raman lightis collected by another probe 640, which is placed adjacent to the lightdelivery device 600. In this scheme, the probe 630 and 640 can beconventional Raman probes with optical components designed to collectthe Raman scattered light from a small area of the sample or they canhave a similar structure as the light delivery and collection device inFIG. 1A, which is designed to collect the Raman scattered light from alarge area of the sample. Alternatively, the conventional Raman probe640 may be used for delivering the excitation light to the sample toexcite Raman scattered light and the light delivery and collectiondevice 600 may be used for collecting the Raman scattered light.

FIG. 7 illustrates a third exemplary embodiment of the light deliveryand collection device. Here the light delivery and collection device 700comprises a reflective cavity 702 which is made of a solid opticalmaterial 703 with a reflective coating 701. The reflective coating 701has two openings, which form the first aperture 704 and the secondaperture 706 of the reflective cavity 702. The light delivery andcollection device 700 further comprises a receptacle 718 which isconfigured to receive a probe 720. The probe 720 receives excitationlight from a light source and focuses the excitation light at the firstaperture 704 of the reflective cavity 702 and thereby delivers theexcitation light 714 into the reflective cavity 702. In a similar way asshown in FIG. 1A, the excitation light 714 excites Raman scattering fromthe sample 708 at the second aperture 706 of the reflective cavity 702.The reflective cavity 702 reflects the excitation light that isreflected and/or back-scattered from the sample and redirects it towardsthe sample. In addition, it reflects the Raman scattered light from thesample unless the Raman scattered light either emits from the firstaperture 704 to be collected by the probe 720 and then measured with aspectrometer device (not shown) to obtain a Raman spectrum of the sample708, or re-enters the sample 708 and be re-scattered by the sample 708at the second aperture 706. The optical material 703 is preferablytransparent to the excitation light 714 and the Raman scattered light716. It may have a refractive index profile which is spatiallyheterogeneous, hence causing changes in the propagation direction of theexcitation light and the Raman light. As one example, the opticalmaterial 603 may have a gradient-index (GRIN) profile with a parabolicvariation of refractive index such that it functions as an optical lens.When the effective focal length of this GRIN lens is equal to the lengthof the reflective cavity 702, the excitation light 714 from the firstaperture 704 will be collimated by the GRIN lens when it reaches thesecond aperture 706, which in turn increases the penetration depth ofthe excitation light into the sample 708.

FIG. 8 illustrates a slight variation of the third exemplary embodimentof the light delivery and collection device. In this variation, thelight delivery and collection device 800 comprises a reflective cavity802 which is made of a solid optical material 803 having a curved endsurface 826. The end surface 826 and the other surfaces 801 of theoptical material 803 may have reflective coatings reflecting atdifferent wavelengths. As one example, the end surface 826 may reflectthe excitation light and the other surfaces 801 may reflect the Ramanlight such that the excitation light and the Raman light are reflectedby two differently shaped reflective cavities.

The light delivery and collection device as disclosed above may beutilized to improve the excitation and collection efficiency for avariety of spectroscopic measurements, including Raman spectroscopy andBrillouin spectroscopy, where a shift in wavelength of the inelasticallyscattered light provides the structural information of the subjectsample, as well as fluorescence and phosphorescence spectroscopy, wherethe absorption of excitation light at a shorter wavelength and emissionof fluorescent light at a longer wavelength reveals the electronic andvibrational state information of the subject sample.

FIG. 9 and FIG. 10 show two examples of utilizing the light delivery andcollection device for measuring the Raman spectra of diffuselyscattering samples contained inside diffusely scattering containers.

FIG. 9A shows the Raman spectrum of sodium benzoate powder contained ina white plastic bottle, which is measured with the aid of a lightdelivery and collection device as shown in FIG. 1A. FIG. 9B shows themeasured Raman spectrum of the plastic bottle by removing the lightdelivery and collection device and focusing the laser beam directly onthe surface of the plastic bottle. By properly scaling the spectrum inFIG. 9B and then subtracting the scaled spectrum from the spectrum inFIG. 9A, one can obtain a calculated Raman spectrum of the sodiumbenzoate powder as shown in FIG. 9C. Comparing this spectrum with theRaman spectrum shown in FIG. 9D, which is collected directly from purelysodium benzoate powder, it can be seen that the calculated spectrum isclose enough to the spectrum of the pure sodium benzoate powder. Byoptimizing the mathematical algorithm of extracting the spectrum of thecontainer, it is possible to further improve the quality of the obtainedspectrum of the sample. Alternatively, mixture analysis can be performeddirectly using spectrum in FIG. 9A to identify the material makeup ofthe sample as a whole, including the container and the content inside.

Various mixture spectral analysis algorithms exist to accomplish suchtasks. With prior knowledge of the container material, the chemicalcomposition of the content inside can be determined. In yet anotherimplementation, the container spectrum in FIG. 9B can be designated as acomponent, and a modified mixture analysis method can be used toidentify the remaining components that make up the spectrum in FIG. 9A.

FIG. 10 illustrates how the light delivery and collection device enablesmaterial identification by means of Raman spectroscopy through adifferent kind of packaging material, i. e. a brown paper envelope. FIG.10A shows the Raman spectrum of a D(+)-Glucose sample contained in thebrown envelope, which is measured with the aid of a light delivery andcollection device as shown in FIG. 1A. FIG. 10B shows the Raman spectrumobtained without the device and with the excitation beam focused on thebrown envelope. FIG. 10C shows the Raman spectrum of the D(+)-Glucosesample measured in absence of the brown paper envelope. Here the brownenvelope spectrum in FIG. 10B displays the signature of cellulose on topof a high level of fluorescence. The signature of the glucose content isalmost completely absent. In contrast, the Raman spectrum obtained withthe light delivery and collection device is almost entirely ofD(+)-Glucose, with a relatively weak contribution from the cellulose. Inthis case, the material inside the packaging material can be directlyidentified by searching through a spectral library.

FIG. 11 illustrates how the light delivery and collection device used intransmission mode enables the measurement of bulk material property.Here the sample is an ibuprofen tablet (Advil, 200 mg) purchased from alocal drug store. The tablet has a brown colored coating. The spectrumin FIG. 11A is obtained in transmission mode using the configurationshown in FIG. 4; the spectrum in FIG. 11B is obtained in reflection modeusing the configuration shown in FIG. 1A; and the spectrum in FIG. 11Cis obtained in reflection mode without the aid of the light delivery andcollection device. The spectrum in FIG. 11C consists of features mostlyfrom the coating of the tablet, while the transmissive Raman spectrum inFIG. 11A consists almost entirely of the drug material inside thecoating. The spectrum in FIG. 11B is similar to the spectrum in FIG.11A, but has relatively more contribution from the coating. To thoseskilled in the art, it is known that the transmission mode measures theRaman signal throughout the entire thickness of the sample, therefore ismore advantageous when the bulk property of the sample as a whole is ofinterest.

In the foregoing specification, specific embodiments of the presentinvention have been described. However, one of ordinary skill in the artappreciates that various modifications and changes can be made withoutdeparting from the scope of the present invention as set forth in theclaims below. Accordingly, the specification and figures are to beregarded in an illustrative rather than a restrictive sense, and allsuch modifications are intended to be included within the scope ofpresent invention. The benefits, advantages, solutions to problems, andany element(s) that may cause any benefit, advantage, or solution tooccur or become more pronounced are not to be construed as a critical,required, or essential features or elements of any or all the claims.The invention is defined solely by the appended claims including anyamendments made during the pendency of this application and allequivalents of those claims as issued.

What is claimed is:
 1. An apparatus for performing spectroscopicanalysis of a subject, the apparatus comprising: a light source forproducing excitation light at a first wavelength; a reflective cavitywith a specular reflective surface, the reflective cavity having a firstaperture and a second aperture, the second aperture is configured to beapplied to the subject such that the reflective cavity substantiallyforms an enclosure covering an area of the subject; one or more opticcomponents configured to focus the excitation light at the firstaperture of the reflective cavity to deliver the excitation light intothe reflective cavity, wherein the excitation light projects onto thesecond aperture of the reflective cavity and enters and interacts withthe covered area of the subject and produces signal light at a secondwavelength, wherein the reflective cavity reflects the excitation lightand signal light which is reflected or back-scattered from the coveredarea of the subject and causes said reflected or back-scatteredexcitation light and signal light to re-enter the covered area of thesubject at the second aperture of the reflective cavity, except saidreflected or back-scattered excitation light and signal light that exitsthe reflective cavity through the first aperture of the reflectivecavity, and wherein the first aperture is sized substantially just largeenough to encompass the beam waist of the focused excitation light; anda spectrometer device for collecting and measuring an optical spectrumof the signal light.
 2. The apparatus of claim 1, wherein thespectrometer device collects the signal light from the first aperture ofthe reflective cavity.
 3. The apparatus of claim 1, wherein thereflective cavity is made of a material having high reflectivity to theexcitation light and signal light.
 4. The apparatus of claim 1, whereinthe reflective cavity has a surface coating with high reflectivity tothe excitation light and signal light.
 5. The apparatus of claim 4,wherein the surface coating is a metal coating.
 6. The apparatus ofclaim 4, wherein the surface coating is a dielectric coating.
 7. Theapparatus of claim 1, wherein the reflective cavity comprises at leastone additional aperture.
 8. The apparatus of claim 1, wherein the secondaperture of the reflective cavity is at least two times as large as thefirst aperture of the reflective cavity in area.
 9. The apparatus ofclaim 1, further comprising an optical window covering the secondaperture of the reflective cavity, wherein the optical window istransparent to the excitation light and signal light.
 10. The apparatusof claim 1, wherein the reflective cavity is formed by a solid opticalmaterial having a reflective coating.
 11. The apparatus of claim 10,wherein the solid optical material has a spatially heterogeneousrefractive index profile.
 12. A method for performing spectroscopicanalysis of a subject, the method comprising the steps of: producingexcitation light at a first wavelength; providing a reflective cavitywith a specular reflective surface, the reflective cavity having a firstaperture and a second aperture; applying the second aperture of thereflective cavity to the subject such that the reflective cavitysubstantially forms an enclosure covering an area of the subject;providing one or more optic components configured to focus theexcitation light at the first aperture of the reflective cavity todeliver the excitation light into the reflective cavity, wherein theexcitation light is adapted to project onto the second aperture of thereflective cavity and enter and interact with the covered area of thesubject and to produces a signal light at a second wavelength, whereinthe reflective cavity reflects the excitation light and signal lightwhich is reflected or back-scattered from the covered area of thesubject and causes said reflected or back-scattered excitation light andsignal light to re-enter the covered area of the subject at the secondaperture of the reflective cavity, except said reflected orback-scattered excitation light and signal light that exits thereflective cavity through the first aperture of the reflective cavity,and wherein the first aperture is sized substantially just large enoughto encompass the beam waist of the focused excitation light; andmeasuring an optical spectrum of the signal light.
 13. The method ofclaim 12, wherein the reflective cavity is made of a material havinghigh reflectivity to the excitation light and signal light.
 14. Themethod of claim 12, wherein the reflective cavity has a surface coatingwith high reflectivity to the excitation light and signal light.
 15. Themethod of claim 14, wherein the surface coating is a metal coating. 16.The method of claim 14, wherein the surface coating is a dielectriccoating.
 17. The method of claim 12, wherein the second aperture of thereflective cavity is at least two times as large as the first apertureof the reflective cavity in area.
 18. The method of claim 12, whereinthe reflective cavity is formed by a solid optical material having areflective coating.
 19. The method of claim 18, wherein the solidoptical material has a spatially heterogeneous refractive index profile.20. A method for performing spectroscopic analysis of a subject, themethod comprising the steps of: producing excitation light at a firstwavelength; delivering the excitation light to a first side of thesubject and causing the excitation light to enter and interact with thesubject to produce signal light at a second wavelength, wherein theexcitation light and signal light at least partially transmits from thefirst side to a second side opposite to the first side of the subject;providing a reflective cavity with a specular reflective surface, thereflective cavity having a first aperture and a second aperture;applying the second aperture of the reflective cavity to the second sidethe subject such that the reflective cavity substantially forms anenclosure covering an area on the second side of the subject, whereinthe reflective cavity reflects said transmitted excitation light andsignal light and causes said transmitted excitation light and signallight to re-enter the covered area of the subject at the second apertureof the reflective cavity, except said transmitted excitation light andsignal light that exits the reflective cavity through the first apertureof the reflective cavity, and wherein the first aperture is sizedsubstantially just large enough to encompass the beam waist of theexcitation light; and measuring an optical spectrum of the signal lightemitted from the first aperture of the reflective cavity.
 21. A methodfor performing spectroscopic analysis of a subject having a surfacelayer and a sub-surface layer of different materials, the methodcomprising the steps of: producing excitation light; providing areflective cavity with a specular reflective surface, the reflectivecavity having a first aperture and a second aperture; applying thesecond aperture of the reflective cavity to the subject such that thereflective cavity substantially forms an enclosure covering an area ofthe subject; delivering the excitation light through the first apertureto be projected onto the second aperture of the reflective cavity andcausing the excitation light to enter and interact with the covered areaof the subject to produce a first signal light, wherein the reflectivecavity reflects the excitation light and first signal light which isreflected or back-scattered from the covered area of the subject andcauses said reflected or back-scattered excitation light and firstsignal light to re-enter the covered area of the subject at the secondaperture of the reflective cavity, except said reflected orback-scattered excitation light and first signal light that exits thereflective cavity through the first aperture of the reflective cavity,and wherein the first aperture is sized substantially just large enoughto encompass the beam waist of the excitation light; measuring the firstsignal light to obtain a first optical spectrum of the subject whichcontains information of both the surface layer and the sub-surface layerof the subject; removing the reflective cavity and focusing theexcitation light to the surface layer of the subject to excite a secondsignal light from the subject, and measuring the second signal light toobtain a second optical spectrum of the subject which mainly containsinformation of the surface layer of the subject; and analyzing adifference between the first optical spectrum and the second opticalspectrum to identify the material of the sub-surface layer.